Fig. 2

Histological characteristics of patellar ligaments. Photomicrographs illustrating characterization of patellar ligament cellularity (A—C; all obtained at 40 × magnification); endotenon thickness and vascularity (D – F); and endotenon fatty infiltration (G – I; all obtained at 10 × magnification). A Normal fascicle cellularity; scattered tenocytes are seen within the fascicles. B Hypercellularity; areas of tenocyte clustering. C Hypocellularity; areas almost devoid of cells. Areas of hypocellularity coincided with areas of metaplastic tenocytes / chondroid metaplasia. D Thin endotenon (40 × magnification). E Distinct endotenon with discrete vessels (40 × magnification). F Distinct endotenon with prominent vessels (10 × magnification). G Slight endotenon fatty infiltration. H Moderate fatty infiltration. I Marked fatty infiltration